With regard to a method for the formation of diamond, a high-pressure synthesis, an explosion synthesis, a gas-phase synthesis, etc. have been known (refer, for example, to Non-Patent Document 1). Among the above, a gas-phase synthesis was invented in the sixtieth and improvements have been carried out up to now. In the Non-Patent Document 2, there is a description that diamond of several μm is formed on a plate of 300 mm×300 mm. In Non-Patent Document 3, there is a description that atmospheric pressure for a gas-phase synthesis which is usually as low as 0.1 atmosphere or less is raised up to 3 atmospheres whereby a forming rate of 450 μm per hour is achieved.
In the Patent Document 1, there is a description that a diamond-like film is formed at the rate of 150 μm per minute using in-liquid plasma means.    [Non-Patent Document 1] “Thin Film of Diamond” by Sugao Otsuka; edited by the Japanese Surface Science Society; published by Kyoritsu Shuppan    [Non-Patent Document 2] Tsukawa, New Diamondo, Vol. 73 (2004), page 16    [Non-Patent Document 3] Hiromichi Toyota, Seimitsu Kogaku Kaishi, Vol. 69, No. 10 (2003), pages 1444 to 1448    [Patent Document 1] Gazette of Japanese Patent Laid-Open No. 2004-152523